City have already brought Txiki Begiristain and Ferran Soriano to the club from Barcelona as director of football and chief executive respectively.
And according to Rosell, the Premier League champions are keen to bring more of the Catalan club's staff to the Etihad Stadium.
"Manchester City have indeed launched an offensive to lure a number of people away from Barcelona," Rosell told RAC1.
"We're talking about people at all levels of the Barca structure, not just players. Their attempts have been unsuccessful, though, as our employees are happy here.
"There have been contacts, but we have a fantastic group of people and nobody wants to go."
Rosell also urged Rosell to act professionally, saying: "I had hoped that he would not use the information he gathered about Barcelona during his time here to help another club become bigger, but he seems to disagree with me.
"I would like it if the relationship between both clubs was a bit better and more transparent."